Drive Herald edits via transactions

Summary: This is kinda bad in terms of UI (It just makes a json of the thing and diffs that), but it's a start.

Test Plan: edit rule, create rule, add/remove/edit conditions, actions

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15542